scholarly journals Computations of Flow and Heat Transfer in a Channel With Rows of Hemispherical Cavities

1999 ◽  
Author(s):  
Y.-L. Lin ◽  
T. I-P. Shih ◽  
M. K. Chyu
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Wall Functions ◽  
Time Stepping ◽  
Flow And Heat Transfer ◽  
A Cell ◽  
Volume Method

Computations were performed to investigate the three-dimensional flow and heat transfer in a high aspect ratio channel in which one or two wall are lined with four rows of hemispherical cavities arranged in a staggered fashion with two Reynolds numbers (23,000 and 46,000). The focus is on understanding the flow induced by cavities and how that flow affects surface heat transfer. Computed results were compared with available experimental data. This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy closed by the low Reynolds number shear-stress transport k-ω turbulence model (wall functions were not used). Solutions were generated by a cell-centered finite-volume method that uses third-order accurate flux-difference splitting of Roe with limiters, multigrid acceleration of a diagonalized ADI scheme with local time stepping, and patched/overlapped structured grids.

scholarly journals Computations of Film Cooling From Holes With Struts

1999 ◽  
Author(s):  
T. I-P. Shih ◽  
Y.-L. Lin ◽  
M. K. Chyu ◽  
S. Gogineni
Keyword(s):  
Film Cooling ◽  
Computational Study ◽  
Three Dimensional ◽  
Protective Layer ◽  
Navier Stokes ◽  
Time Stepping ◽  
Cooling Hole ◽  
A Cell ◽  
Volume Method ◽  
Film Cooling Holes

Computations were performed to study the three-dimensional flow and heat transfer on a flat plate cooled by jets, injected from a plenum through one row of film-cooling holes in which each hole is fitted with a strut in the form of a circular cylinder. Three different configurations of the film-cooling hole were investigated: without strut, with streamwise strut, and with spanwise strut. For all configurations, the film-cooling holes are inclined at 35°, and the coolant-to-mainflow density and mass-flux ratios are 1.6 and 0.5, respectively. The focus of this study is to understand how struts in holes affect film cooling jets and their interactions with the mainflow in forming a protective layer of cooler fluid over the plate. This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy. Effects of turbulence was modeled by a low Reynolds number k-ω closure known as the shear-stress-transport (SST) model. Solutions were generated by a cell-centered finite-volume method that uses third-order accurate flux-difference splitting of Roe with limiters, multigrid acceleration of a diagonalized ADI scheme with local time stepping, and patched/overlapped structured grids. In the computations, the flow is resolved not just in the cooling-jet/mainflow interaction region, but also inside the film-cooling holes and in the plenum. Computed results for adiabatic effectiveness for the case without struts were compared with experimental data, and reasonably good agreements were obtained.

CFD Simulations of an Axisymmetric Mixed-Compresssion Inlet With Bleed Through Discrete Holes

2003 ◽  
Author(s):  
David B. Benson ◽  
Tom I.-P. Shih ◽  
David O. Davis
Keyword(s):  
Computational Study ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Third Order ◽  
Time Stepping ◽  
Sst Turbulence Model ◽  
A Cell ◽  
Volume Method ◽  
Flux Difference ◽  
Bleed Through

CFD simulations were performed to investigate boundary-layer control through bleed patches in an axisymmetric mixed-compression inlet in which the bleed patches are modeled by two global bleed boundary conditions (BCs). In one bleed BC, the locations of the bleed holes are discerned. In the other bleed BC, each row of bleed holes is modeled as a porous surface, where the number of bleed holes in each row is accounted for by adjusting the discharge coefficient to give the correct bleed rate. Results are presented for the predicted bleed rates, pressure on the cowl and centerbody surfaces, and the flow field. Comparisons were made with available experimental data. Also presented is a method based on one-dimensional isentropic and normal shock solutions to get the flow “started” in CFD simulations of critical flow in mixed-compression inlets. This computational study is based on the ensemble-averaged conservation equations of mass (continuity), momentum (compressible Navier-Stokes), and total energy closed by shear-stress transport (SST) turbulence model, where integration is to the wall. Solutions were generated by a cell-centered finite-volume method that uses third-order accurate flux-difference splitting of Roe with limiters, multigrid acceleration of a diagonalized ADI scheme with local time stepping, and patched/overlapped structured grids.

Effects of Gap Leakage on Fluid Flow in a Contoured Turbine Nozzle Guide Vane

2000 ◽  
Author(s):  
Y.-L. Lin ◽  
T. I-P. Shih ◽  
M. K. Chyu ◽  
R. S. Bunker
Keyword(s):  
Computational Study ◽  
Guide Vane ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Hot Gas ◽  
Nozzle Guide Vane ◽  
A Cell ◽  
Nozzle Guide ◽  
Volume Method

Computations were performed to study the three-dimensional flow in a nozzle guide vane with leakage issuing from a narrow gap with a backward-facing step located upstream of the airfoil on each endwall. The nozzle guide vane investigated has one flat and one contoured endwall. For the contoured endwall, two configurations of the same contouring profile were investigated with and without gap leakage. In one configuration, all contouring is upstream of the airfoil passage. In the other, the contouring starts upstream of the airfoil passage and continues through it. Results obtained show that when there is gap leakage, secondary flows are reduced at all endwalls for both nozzle configurations investigated. Without gap leakage, secondary flows are reduced only on the contoured endwall in which the contouring started upstream of the airfoil passage and continued through it. When all of the contouring is located upstream of the airfoil passage, there is considerable hot gas ingestion into the gap at both endwalls. When the contouring starts upstream of the airfoil passage and continues throught it, hot gas ingestion was minimal at the contoured endwall and greatly reduced at the flat endwall. This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy. Effects of turbulence were modeled by the low Reynolds number shear-stress transport k-ω model. Solutions were generated by a cell-centered finite-volume method that uses third-order accurate flux-difference splitting of Roe with limiters and multigrid acceleration of a diagonalized ADI scheme with local time stepping on patched structured grids.

Flow and Heat Transfer in the Tip-Turn Region of a U-Duct Under Rotating and Non-Rotating Conditions

2011 ◽  
Author(s):  
S.-Y. Hu ◽  
X. Chi ◽  
T. I.-P. Shih ◽  
K. M. Bryden ◽  
M. K. Chyu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Computational Study ◽  
Reynolds Numbers ◽  
Coolant Temperature ◽  
Internal Cooling ◽  
Wall Functions ◽  
Flow And Heat Transfer ◽  
Aspect Ratios ◽  
Turn Region

CFD simulations were performed to study the flow and heat transfer in a U-duct, relevant to internal cooling of the first-stage turbine component in electric-power-generation, gas-turbine engines. Parameters studied include (1) two aspect ratios of the duct cross section, i.e. H/W = 1 and H/W = 0.25; (2) smooth duct and duct lined with pin fins of height H arranged in a staggered fashion; and (3) two rotational speeds: 0 rpm and 3,600 rpm. In all cases, the wall temperature is 1173 K; the coolant temperature at the U-duct inlet is 623 K; and the back pressure at the exit of the U-duct is 25.17 atm. The Reynolds numbers studied are 150,000 for the duct with the 4-to-1 aspect ratio, and 150,000 and 375,000 for the duct with the 1-to-1 aspect ratio. When there is rotation at 3,600 rpm, the rotational numbers corresponding to these Reynolds numbers and duct aspect ratios are 0.592, 1.64, and 4.11, respectively. Result is presented to show the nature of the flow, the temperature distribution, and the surface heat transfer with focus on the flow and heat transfer in the tip-turn region as a function of the parameters investigated. This computational study is based on 3-D steady RANS. The ensemble-averaged continuity, compressible Navier-Stokes, and energy equations were closed by the thermally perfect equation of state with temperature-dependent gas properties and the two-equation realizeable k-ε turbulence model with and without wall functions.

Effect of Inclination Angle on Three-Dimensional Combined Convective Heat Transfer of Nanofluids in Rectangular Channels

2013 ◽  
Vol 388 ◽  
pp. 176-184
Author(s):  
Hussein A. Mohammed ◽  
Nur Irmawati Om ◽  
Mazlan A. Wahid
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Inclination Angle ◽  
Pure Water ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Flow And Heat Transfer ◽  
Rectangular Channels ◽  
Energy Equations ◽  
Volume Method

Combined convective nanofluids flow and heat transfer in an inclined rectangular duct is numerically investigated. Three dimensional, laminar Navier-Stokes and energy equations were solved using the finite volume method. Pure water and four types of nanofluids such as Au, CuO, SiO2 and TiO2with volume fractions range of 2% φ 7% are used. This investigation covers the following ranges: 2 × 106 Ra 2 × 107, 100 Re 1000 and 30° Θ 60°. The results revealed that the Nusselt number increased as Rayleigh number increased.SiO2nanofluid has the highest Nusselt number while Au nanofluid has the lowest Nusselt number. An increasing of the duct inclination angle decreases the heat transfer.

Characteristics of Fully Developed Flow and Heat Transfer in Channels With Varying Wall Geometry

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Abhishek G. Ramgadia ◽  
Arun K. Saha
Keyword(s):  
Heat Transfer ◽  
Time Dependent ◽  
Navier Stokes ◽  
Fully Developed Flow ◽  
Flow And Heat Transfer ◽  
Collocated Grid ◽  
Wall Profile ◽  
Energy Equations ◽  
Volume Method ◽  
Wall Geometry

Present study focuses on numerical investigation of fully developed flow and heat transfer through three channels having sine-shaped, triangle-shaped, and arc-shaped wall profiles. All computations are performed at Reynolds number of 600. Finite volume method on collocated grid is used to solve the time-dependent Navier–Stokes and energy equations in primitive variable form. For all the geometries considered in the study, the ratios Hmin/Hmax and L/a are kept fixed to 0.4 and 8.0, respectively. The thermal performances of all the three wall configurations are assessed using integral parameters as well as instantaneous, time-averaged and fluctuating flow fields. The geometry with the sinusoidal-shaped wall profile is found to produce the best thermal properties as compared to the triangle-shaped and the arc-shaped profiles though the obtained heat transfer is the highest for the arc-shaped geometry.

The Numerical Prediction of Viscous Flow and Heat Transfer in Tube Banks

1978 ◽  
Vol 100 (4) ◽  
pp. 565-571 ◽  
Author(s):  
B. E. Launder ◽  
T. H. Massey
Keyword(s):  
Heat Transfer ◽  
Viscous Flow ◽  
Stokes Equations ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Substantial Contribution ◽  
Navier Stokes Equations ◽  
Flow And Heat Transfer ◽  
Flow Domain ◽  
Tube Banks

A scheme for handling the numerical analysis of viscous flow and heat transfer in tube banks is presented. It involves the use of a cylindrical network of nodes in the vicinity of the tubes with a Cartesian mesh covering the remainder of the flow domain. The approach has been incorporated into the numerical solving algorithm for the Navier Stokes equations of Gasman, et al. [8]. A number of demonstration calculations is presented including a numerical simulation of the staggered square bank for which Bergelin and co-workers [4, 9] have reported experimental results for pressure drop and heat transfer rate. Agreement between predicted and measured characteristics is satisfactory when account is taken of end and entry effects that are present in the experiments but necessarily omitted from the calculations. Indeed the close agreement of the laminar predictions with measurements extends to Reynolds numbers in excess of 1000, a level at which it has hitherto been supposed that turbulent motion in the fluid made a substantial contribution to friction and heat transfer.

Amplification of three-dimensional perturbations during parallel vortex–cylinder interaction

2007 ◽  
Vol 573 ◽  
pp. 457-478
Author(s):  
X. LIU ◽  
J. S. MARSHALL
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Front Surface ◽  
Inviscid Flow ◽  
Reynolds Numbers ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Flow Features ◽  
Volume Method ◽  
Proper Orthogonal

A computational study has been performed to examine the amplification of three-dimensional flow features as a vortex with small-amplitude helical perturbations impinges on a circular cylinder whose axis is parallel to the nominal vortex axis. For sufficiently weak vortices with sufficiently small core radius in an inviscid flow, three-dimensional perturbations on the vortex core are indefinitely amplified as the vortex wraps around the cylinder front surface. The paper focuses on the effect of viscosity in regulating amplification of three-dimensional disturbances and on assessing the ability of two-dimensional computations to accurately model parallel vortex–cylinder interaction problems. The computations are performed using a multi-block structured finite-volume method for an incompressible flow, with periodic boundary conditions along the cylinder axis. Growth of three-dimensional flow features is examined using a proper-orthogonal decomposition of the Fourier-transformed vorticity field in the azimuthal and axial directions. The interaction is examined for different axial wavelengths and amplitudes of the initial helical vortex waves and for three different Reynolds numbers.

Fluid Flow and Heat Transfer in a Novel Microchannel Heat Sink Partially Filled With Metal Foam Medium

2014 ◽  
Vol 6 (2) ◽  
Author(s):  
E. Farsad ◽  
S. P. Abbasi ◽  
M. S. Zabihi
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Metal Foam ◽  
Three Dimensional ◽  
Numerical Data ◽  
Flow And Heat Transfer ◽  
Cooling Devices ◽  
Volume Method ◽  
Steady Laminar ◽  
Good Agreement

Performance of microchannel heatsink (MCHS) partially filled with foam is investigated numerically. The open cell copper foams have the porosity and pore density in the ranges of 60–90% and 60–100 PPI (pore per inch), respectively. The three-dimensional steady, laminar flow, and heat transfer governing equations are solved using finite volume method. The performance of microchannel heatsink is evaluated in terms of overall thermal resistance, pressure drop, and heat transfer coefficient and temperature distribution. It is found that the results of the surface temperature profile are in good agreement with numerical data. The results show the microchannel heatsink with insert foam appears to be good candidates as the next generation of cooling devices for high power electronic devices. The thermal resistance for all cases decreases with the decrease in porosity. The uniformity of temperature in this heatsink is enhanced compared the heatsink with no foam. The thermal resistance versus the pumping power is depicted, it is found that 80% is the optimal porosity for the foam at 60 PPI with a minimum thermal resistance 0.346 K/W. The results demonstrate the microchannel heatsink partially filled with foam is capable for removing heat generation 100 watt over an area of 9 × 10−6 m2 with the temperature of heat flux surface up to 59 °C.

Conjugate Heat Transfer Analysis of Internally Cooled Configurations

2001 ◽  
Author(s):  
David L. Rigby ◽  
Jan Lepicovsky
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Energy Equation ◽  
Reynolds Numbers ◽  
Heat Transfer Analysis ◽  
Navier Stokes ◽  
The Past ◽  
Flow And Heat Transfer ◽  
Internally Cooled ◽  
Solid Region

This paper describes the addition of conjugate capability to an existing Navier-Stokes code. Also, results are presented for an internally cooled configuration. The code is currently referred to as the Glenn-HT code, because of its origin at the NASA Glenn Research center and its proven ability to predict flow and Heat Transfer. In the past, the code had been called traf3d.mb. The addition of the conjugate capability to the code was accomplished with a minimum amount of changes to the code, with the understanding that if more advanced techniques were required they could be added at a later date. In the solid region, the density is constant and the velocities are of course zero which leaves only a simplified form of the energy equation to be solved. This simplified energy equation is solved using the same method as in the gas regions with only minor changes to the numerical parameters. At the interface between the gas and solid the wall temperature is set so as to produce the same heat flux in each region. Results are presented for a pipe flow to validate the implementation. Numerical and experimental results are then presented for flow over a flat plate that is cooled internally. Flat plate Reynolds numbers in the range 180,000 to 950,000, and coolant channel Reynolds numbers in the range 30,000 to 60,000 are presented.

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